We run with our dash air exclusively. It cools our 32 ft coach very well while driving. We always turn on the Genset and both roof airs about 20 minuetes out from stopping for the night. The coach continues to cool while checking in, getting to the campsite and setting up.
A cool coach and two way radios have kept us happily married for 40 years.

95? Dash a/c would be fine if I don't mind sweating. Otherwise it's gen, roof air, and a 12 volt fan on the floor to my right. If it's really hot I'll turn on the defrost fans and the dash vent on recirculate.

The dash A/C in my coach is 19,000 BTU. Coach is 33 feet. The dash air alone keeps us cool and comfortable to 95 degrees if humid and 100 is dry. Then we turn on generator and rear A/C in addition to dash.

The dash air is not enough if you are in 100 degree plus, you have to run the generator. Too much volume for the dash air to cool. It will throw cool air at your face, but it is best just to start the generator and cool the whole coach. Generators are very economical anyways, about a gallon per hour.

Dash AC designed for a truck cab not the volume of a Class A. Generator spec rate fuel usage at 1/2 gallon an hour which if converted to MPG @60 MPH is 120 MPG. At worst it's a wash in fuel usage but I think I get better overall fuel usage running the generator. As an added bonus the coach is nice and cool when we arrive at the CG.

2006 Hurricane 31D aka 'Moby' the Whale
FCC(SW) US Navy Retired 1980-2003
Stella my Navigator
Bogart the All American RV Dog
and
Cocoui waiting for me at the Rainbow Bridge